Mix together pre-made mashed potatoes (either leftover, made from your favorite recipe, or store bought) with an egg. Scoop into greased muffin tins (regular or shapes). Top with cheese (if desired). Bake at 350* for 10 to 20 minutes until warmed through and golden brown. Serve with toppings as desired. Some examples of toppings are bacon bits, scallions, and sour cream.